An indoor unit for an air conditioner in the prior art has a housing that is constituted by a base plate, a face frame mounted to the base plate, and a panel mounted to the face frame. A heat exchanger and a fan are mounted to the base plate, and a fan wheel of the fan is located at an inner side of the heat exchanger. Even though the face frame is dismounted, the fan wheel cannot be dismounted only if the heat exchanger is also dismounted, because the fan wheel is limited by the heat exchanger and the base plate together, which brings about great inconvenience for a user to dismount the fan wheel. The dismounting and cleaning of the fan wheel cannot be performed by the user, but needs professional help, which results in a high cost.